Chromatography is a set of techniques for separating a mixture into its constituents. For instance, in a liquid chromatography (LC) application, a solvent delivery system takes in a mixture of liquid solvents and delivers the mixture to an autosampler (also called an injection system or sample manager), where an injected sample awaits the arrival of this mobile phase. The mobile phase with the dissolved injected sample passes to a column. By passing the mixture through the column, the various components in the sample separate from each other at different rates and thus elute from the column at different times. A detector receives the separated components from the column and produces an output from which the identity and quantity of the analytes may be determined.
Well-established separation technologies include HPLC (High Performance Liquid Chromatography), UPLC (Ultra Performance Liquid Chromatography), and CO2-based chromatography, such as SFC (Supercritical Fluid Chromatography), gas chromatography (GC), and solvating gas chromatography (SGC). HPLC systems use high pressure, ranging traditionally between 1,000 psi (pounds per square inch) to approximately 6,000 psi, to generate the flow required for liquid chromatography in packed columns. In contrast to HPLC, UPLC systems use columns with smaller particulate matter and higher pressures approaching 20,000 psi to deliver the mobile phase. SFC, GC, and SGC systems use highly compressible mobile phases, which typically employ CO2 as a principle component. To ensure that the CO2 component remains liquid, the CO2 is at elevated pressure and reduced temperature. Because a single pump of the CO2-based system is dedicated to the intake of CO2, however, liquid chromatography systems that are configured for CO2-based chromatography generally cannot also be configured to perform either HPLC or UPLC, without a time and labor intensive reconfiguration of the system.